add "example" dependencies

Author: MedericFourmy

README.md

@@ -33,6 +33,8 @@ cd pym3t
 python -m venv .venv
 source .venv/bin/activate
 pip install .
+# or if you want to run examples
+pip install .[examples]
 ```
 
 # Example scripts

pyproject.toml

@@ -7,8 +7,13 @@ build-backend = "scikit_build_core.build"
 [project]
 name = "pym3t"
 version = "0.0.1"
-requires-python = ">=3.7"
+requires-python = ">=3.8"
 # run time dependencies
-dependencies = [
-    "numpy"
+dependencies = []
+
+[project.optional-dependencies]
+examples = [
+    "numpy<2.0.0", # older numpy-quaternion releases are not compatible with numpy 2.0.0
+    "numpy-quaternion>=2023.0.3",
+    "opencv-python>=4.11.0.86",
 ]